Snap a bunch of keyframes to the cursor?
Within the Dope Sheet and the Graph Editor you can snap the selected keyframes using the snap menu - Key->snap or Shift-S and choose one of several options.



You can de-select all keyframes by pressing A then use box select B to draw a box around the desired keyframes.

The DopeSheet also has 'summary lines' for example the 'Cube' line. Selecting a keyframe in a summary line will select all related keyframes.



Also a common method to align things in blender is to apply a scale of zero.

In the Dope Sheet selecting the keyframes you want to align and pressing S then 0 will align them all to the current frame.

In the Graph Editor you will want to ensure you only affect the frame by scaling the desired points along the x axis (S-X-0). Here they will scale to a frame between the earliest and latest selected, then you probably want to move them to the frame you want (G-X)

The same scaling trick applies to aligning almost anything. Objects in object mode (you need to make sure you turn on manipulate centre points for object alignment), vertices in edit mode, curve points, armature bones, nodes...